Relaxation oscillator frequency accuracy improvement - uses generator of highly stable frequency to determine commutating threshold voltage

摘要

The process is intended for tariff determination in telephone systems, using universal clock pulse generators with counting facilities. The threshold voltage determining the change-over time of each relaxation oscillator is so changed by superposition of a synchronisation pulse train delivered by a highly stable generator, or derived from it by frequency division whose frequency coincides with the relaxation oscillator nominal frequency, that at first it is increased and then reduced. The amplitude of the threshold rise or fall determining the synchronisation range can be varied by changing the superposition resistor.